The phosphatidic acid phosphatase of the chloroplast envelope is located on the inner envelope membrane

AbstractThe envelope from spinach chloroplasts contains an alkaline phosphatidic acid phosphatase which was found to be located on the inner envelope membrane. The diacylglycerol formed by this enzyme from endogenous phosphatidic acid is then used as a substrate for galactolipid synthesis on the inner envelope membrane

Sulfolipid Is a Potential Candidate for Annexin Binding to the Outer Surface of Chloroplast

International audienceUsing a subcellular-specific proteomic approach, we have identified by protein microsequencing, a putative 35-kDa annexin from among the chloroplast envelope polypeptides. To confirm this identification, we demonstrate that (a) a 35-kDa protein, identified as annexin by antibody cross-reactivity, co-purifies with Percoll-purified chloroplasts and their envelope membranes when extracted in the presence of Ca(2+) and (b) the native spinach annexin protein binds to chloroplast-specific lipids in a Ca(2+)-dependent manner. The binding of the spinach annexin to these glycerolipids occurs at similar Ca(2+) concentrations as those, which promote the interaction of annexins to phospholipids in other membranes. Among chloroplast glycerolipids known to be accessible on the cytosolic face (outer leaflet) of the outer envelope membrane, sulfolipid, and probably phosphatidylinositol, would be the sole candidates for a putative Ca(2+)-dependent interaction of annexin with the chloroplast surface

Arabidopsis A BOUT DE SOUFFLE, Which Is Homologous with Mammalian Carnitine Acyl Carrier, Is Required for Postembryonic Growth in the Light

The degradation of storage compounds just after germination is essential to plant development, providing energy and molecules necessary for the building of a photosynthetic apparatus and allowing autotrophic growth. We identified à bout de souffle (bou), a new Arabidopsis mutation. Mutant plants stopped developing after germination and degraded storage lipids, but they did not proceed to autotrophic growth. Neither leaves nor roots developed in the mutant. However, externally added sugar or germination in the dark could bypass this developmental block and allowed mutant plants to develop. The mutated gene was cloned using the transposon Dissociation as a molecular tag. The gene coding sequence showed similarity to those of the mitochondrial carnitine acyl carriers (CACs) or CAC-like proteins. In animals and yeast, these transmembrane proteins are involved in the transport of lipid-derived molecules across mitochondrial membranes for energy and carbon supply. The data presented here suggest that BOU identifies a novel mitochondrial pathway that is necessary to seedling development in the light. The BOU pathway would be an alternative to the well-known glyoxylate pathway

Pea seed mitochondria are endowed with a remarkable tolerance to extreme physiological temperatures

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceMost seeds are anhydrobiotes, relying on an array of protective and repair mechanisms, and seed mitochondria have previously been shown to harbor stress proteins probably involved in desiccation tolerance. Since temperature stress is a major issue for germinating seeds, the temperature response of pea ( Pisum sativum) seed mitochondria was examined in comparison with that of mitochondria from etiolated epicotyl, a desiccation-sensitive tissue. The functional analysis illustrated the remarkable temperature tolerance of seed mitochondria in response to both cold and heat stress. The mitochondria maintained a well-coupled respiration between -3.5 degrees C and 40 degrees C, while epicotyl mitochondria were not efficient below 0 degrees C and collapsed above 30 degrees C. Both mitochondria exhibited a similar Arrhenius break temperature at 7 degrees C, although they differed in phospholipid composition. Seed mitochondria had a lower phosphatidylethanolamine-to-phosphatidylcholine ratio, fewer unsaturated fatty acids, and appeared less susceptible to lipid peroxidation. They also accumulated large amounts of heat shock protein HSP22 and late-embryogenesis abundant protein PsLEAm. The combination of membrane composition and stress protein accumulation required for desiccation tolerance is expected to lead to an unusually wide temperature tolerance, contributing to the fitness of germinating seeds in adverse conditions. The unique oxidation of external NADH at low temperatures found with several types of mitochondria may play a central role in maintaining energy homeostasis during cold shock, a situation often encountered by sessile and ectothermic higher plant

Isolation and characterization of Chlamydomonas mutants deficient in the plastid ycf10 open reading frame

International audienceThe complete DNA sequences of a dozen plastid genomes have been determined and they have revealed the existence of approximately 120 genes that can be divided in three major groups. The first group (approximately 50 genes) corresponds to sequences required for plastid transcription and translation. The second group (approximately 40 genes) codes for components of the photosynthetic apparatus. The last group contains many open reading frames of unknown function (for review, see [1]). Some of these are species-specific and designated as ORFs. Those that are conserved in algae and in higher and lower plants have been designated ycf for “hypothetical chloroplast open reading frame”. Chloroplast reverse genetics coupled with biophysical and biochemical analysis has become a powerful tool for analyzing the function of chloroplast-encoded proteins. Several of these ORFs of unknown function have been inactivated in Chlamydomonas reinhardtii and tobacco by biolistic transformation (for review, see [2]). This paper summarizes the characterization of a Chlamydomonas ycf10-deficient mutant. An unusual feature of this chloroplast gene is that it encodes a plastid envelope protei

The Biochemical Machinery of Plastid Envelope Membranes

International audienc